Bharti Jayshankar
November 30, 2024: Researchers say a concerning trend of extreme heat events has emerged across the globe, where certain regions are experiencing unprecedented heat waves that far exceed predictions from climate models. The research, published in the Proceedings of the National Academy of Sciences (PNAS), maps regions worldwide that have been repeatedly hit by extreme heat waves, resembling “giant, angry skin blotches” on every continent except Antarctica.
This phenomenon, referred to as “tail-widening,” poses serious questions about the reliability of current climate models to predict regional climate risks based on global mean temperature changes.
Implications for climate models
The models tend to underestimate the frequency and intensity of extreme heat events, particularly in high-latitude regions. For instance, while climate models indicate that approximately 55% of land areas exhibit positive tail width trends, only 48% of these trends are supported by observational data. Furthermore, significant differences arise when comparing observed data with model predictions; only 16.3% of land-weighted positive trends were statistically significant in observational data compared to just 10.5% in models.
Heat waves have resulted in tens of thousands of deaths, devastated crops and forests, and triggered catastrophic wildfires. Lead author Kai Kornhuber, from Columbia University’s Lamont-Doherty Earth Observatory, states, “These regions become temporary hothouses,” indicating a worrying shift in climate dynamics.
With 2023 recorded as Earth’s hottest year—averaging 2.12 degrees Fahrenheit above the 20th-century average—this research underscores an urgent need to reevaluate our understanding of climate change impacts.
Key findings
The most intense and consistent signals of extreme heat are observed in northwestern Europe, where heat waves contributed to approximately 60,000 deaths in 2022 and 47,000 deaths in 2023.
A notable example includes a nine-day heat wave in June 2021 that shattered records in the U.S. Pacific Northwest and southwestern Canada, with temperatures soaring by 30 degrees Celsius (54 degrees Fahrenheit) in some areas.
The study identifies regions such as central China, Japan, the Arabian Peninsula, and parts of eastern Australia as particularly hard-hit by these extreme temperature spikes.
While some areas are experiencing alarming increases in maximum temperatures, others show lower extremes than predicted. Regions like the north-central United States and parts of Canada are seeing heat increases but at rates comparable to or less than what climate models suggest.
Causes and implications
The causes behind these extreme heat waves remain complex and not fully understood. Previous studies have linked such events to disturbances in the jet stream—specifically, Rossby waves that transport hot air from southern regions into temperate zones. Rapid Arctic warming exacerbates this disruption, destabilizing weather patterns.
A recent report indicated that heat-related deaths have more than doubled since 1999, with 2,325 fatalities recorded in 2023 alone. This alarming trend has prompted discussions about naming heat waves similar to hurricanes to raise public awareness and encourage governmental preparedness. Kornhuber warns that “we’re not built for them,” highlighting the urgent need for adaptation strategies as these unprecedented heat events continue to escalate.
The study calls for further research into local climatic factors contributing to these extremes and emphasizes the importance of improving climate models for better prediction and mitigation strategies.
